Correct Answer: B

Rationale: The word 'sanguinary' is derived from the Latin word 'sanguinarius,' meaning bloodthirsty or bloodshed. In the context of the sentence, 'sanguinary' is used to indicate that surgery is a procedure that involves bloodshed. Therefore, the correct answer is B. Choice A ('Hopeful or cheerful') is incorrect because 'sanguinary' does not convey a positive or cheerful meaning. Choice C ('Difficult and protracted') is incorrect as 'sanguinary' specifically relates to blood or bloodshed, not difficulty or prolongation. Choice D ('Tricky and sensitive') is incorrect as 'sanguinary' does not imply trickiness or sensitivity but rather the presence of blood or bloodshed.

Correct Answer: B

Rationale: The correct answer is B. parietal. The parietal bone is one of the eight bones that form the human skull. It is located near the top of the skull and forms the sides and roof of the cranium. The parietal bones come together at the top of the skull in a structure called the sagittal suture. Choices A, C, and D are incorrect as they do not refer to any cranial bone. 'Partial' means incomplete, 'pariah' refers to an outcast or social reject, and 'parhelion' is a bright spot appearing on either side of the sun.

Correct Answer: C

Rationale: In the context of the sentence, the word 'placebo' refers to a substance or treatment that resembles a real medical treatment but has no therapeutic effect. It is used as a standard against which the effects of the experimental drug are compared. A placebo is typically included in a control group in medical research to evaluate the actual effects of the experimental drug. Therefore, in this scenario, the placebo serves as a control to gauge the effectiveness of the experimental drug, making choice C the correct answer. Choices A, B, and D are incorrect because a placebo is not a fallback, substitute, or curative treatment in this context.

Correct Answer: A

Rationale: In this context, the word 'coterie' refers to a small group of people who share similar interests or activities, typically a close-knit circle of friends. The other choices are incorrect. 'An extended family' refers to relatives beyond the nuclear family, 'an engaged person' is someone committed to be married, and 'a manager or director' are job roles unrelated to the context of the sentence.

Correct Answer: A

Rationale: The abbreviation PDR stands for Physician's Desk Reference, which is a widely used book containing information about prescription drugs, including their uses, side effects, and dosages. Therefore, the abbreviation PDR is associated with drugs. Choices B, C, and D are incorrect because PDR specifically relates to drugs and not procedures, books, or muscle groups.